The most common prior art toilet bowl includes a water tank reservoir positioned above the toilet bowl, whereas when the water is released, gravity is used to flush the toilet bowl. There is no sealed valve at the exit end of the toilet bowl and a siphon structured is used to prevent the return of flush water and waste and to prevent odor. When a control handle is manually operated, water in the tank passes into a toilet bowl that may contain waste, to flush the waste through an upper trap and through a passage leading to a drain pipe. The water-filled upper trap prevents sewer gas from passing into the washroom.
Some prior art water tanks include water saver mechanisms to reduce the amount of water passed into the bowl in each flushing, and uses a smaller toilet bowl to enable the contents of the bowl to be flushed out using less water. Water saving tanks often include to mechanical switches, one for the full tank release and on for releasing a portion of the water stored in the tank. Flush tanks often suffer from leaks and dual flush toilet double the probability of leaking from a flush valve to occur.
The water tank further includes mechanism, including many moving parts, gaskets, etc., that often break down and thus requires maintenance.